Given their preference for working with pre-recorded scores, the Quay Brothers were natural choices for the BBC'sSound On Film initiative, which showcased collaborations between filmmakers and composers. Discounting filmed stage works, In Absentia was the first authentic Quay film since Institute Benjamenta (1995), but attracted most attention because it was a collaboration with Karlheinz Stockhausen, elder statesman of the twentieth-century musical avant-garde.

It was sourced from Zwei Paare ('Two Pairs'), an electronic piece originally composed for the opera Freitag in 1991. Long-term admirers of Stockhausen's work (one of their earliest professional commissions was the cover design of a 1973 book, Stockhausen: Conversations with the Composer), the Quays agreed to make the film before hearing the music. But when the recording arrived, they were disconcerted to discover that it consisted almost entirely of electronic howls and distorted human cries, with very few melodic, harmonic or rhythmic elements to latch on to.

But this relentlessness fitted their chosen subject, which was a depiction of the mental state of one Emma Hauck (1878-1920). Diagnosed with dementia praecox, she was incarcerated in Heidelberg's psychiatric clinic on her thirtieth birthday in 1909. There, she wrote obsessively to her long-absent husband, the letters consisting of barely legible scrawls rendered doubly incomprehensible by being layered on top of one another. The Quays had encountered her letters at an exhibition at London's Hayward Gallery, Beyond Reason (1996-7), which showcased work from the Hans Prinzhorn collection of artworks and artifacts created by the inhabitants of mental institutions.

But Hauck herself doesn't appear properly until halfway through the film, by which time her mental state has already been established by means of time-lapse studies of light patterns moving around her room, its furniture and windows, as well as low-angle shots of a childlike automaton aimlessly kicking its legs to and fro. Much of this is shot in black and white, with occasional flashes to colour shots of a demonic, horned, insectoid creature.

When Hauck appears (albeit mostly seen from behind), the film's focus narrows, with great emphasis placed on extreme close-ups of the objects central to her existence: the pencils, the sharpener, the paper, her cramped, clenching hands, blackened fingernails, endless stubs of broken-off lead, and finally the letters themselves, packaged up and 'posted' uselessly into a grandfather clock. It's one of the most unflinching depictions of psychosis on film, and one of the most unnervingly convincing.